1. Field of the Invention
The present invention relates to a motor speed variator and a driving method thereof, and more particularly to a motor speed variator and a driving method thereof for controlling the operating speed of a fan.
2. Description of Related Art
In the present wireless remote control fan speed variation systems, different capacitances are used for achieving a step-down function and a voltage for controlling a motor, so as to achieve the function of changing the operating speed of the fan. However, this method is restricted by the parameters of the motor. If a same capacitance goes with different motors, then these motors will have different rotary speeds, and thus it will be difficult for users to choose an appropriate capacitance for a future upgrade of a fan system originally having no speed variation function. The fans of this sort have significant impact on the DIY market. As to manufacturers, different motors with different capacitances are required and create some difficulty for the production of motors as well as a burden of carrying the inventory of components. As to functions, it is not feasible to lower the voltage by using different capacitors to achieve the stepless speed variation function because of the cost and size of the integrated circuits.
A remote control fan speed variation system as described below uses an industrial hanging fan for example and illustration. Industrial hanging fans have been used extensively since the 1950's, and the sale of hanging fans in Europe and America peaked in the 1970's. Active exports also brought a breakthrough to the hanging fan development, and revolutionary hanging fan products come with air conditioning, indoor illumination, and accelerated air cooling functions; and thus such hanging fans are protected by patents and have become an indispensable product for domestic life.
Since the hanging fan has become an integral part of our life and our living quality is thereby increased, the stability, safety, comfort of use, and control of the hanging fan have become main factors for consideration. Development of a stable and high-quality hanging fan system is a subject for manufacturers to provide tremendous convenience and comfort to users. The development technology is advanced, but the way of achieving the stepless speed variation, remote control and low noise for the rotation of the hanging fans has become a major issue of the product. Although there are brushless DC (BLDC) motor related products in the Japan market that can achieve the foregoing functions, they are very expensive. The traditional hanging fan speed variation system can be implemented by the following ways:
1. The concept of using a coupled transformer on a wall for the control is adopted to achieve a stepless speed variation function, but its volume is too large, and such method is generally used in developing countries such as India.
2. Different coils are used for a motor to achieve a step speed variation function, and such method usually comes with three speeds. However, the winding of the motor is complicated, and the motor produces noise due to the imbalanced coil of the motor. This method is commonly used in Taiwan.
3. The voltage of different capacitors is reduced to achieve the speed variation function, and thus the voltage of the motor will be changed, and the speed variation speed can be achieved. However, such method cannot achieve the stepless speed variation function.
4. The thyristor of an alternating silicon controlled switch (TRIAC) is used to modulate the phase of the voltage, so that the rotary speed of the motor can be controlled. This method also produces noise and cannot be used for a low-speed operation.
The aforementioned four methods used in the industry not only increase the volume of the product, but also fail to achieve the stepless speed variation or eliminate noise.